FIELD OF INVENTION
The present invention relates to a continuously variable transmission, and more particularly to a transmission which can convert and transmit the power of an engine to comply with the load on the output shaft without changing gears with a shift lever.
In general, a transmission device converts and transmits the power generated by an engine to comply with the load placed on the output shaft. Prior art transmission devices utilize a hand-operated shift lever and a foot-operated clutch to cut the power between the input side receiving the power from the engine and the transmission device in order to accomplish a shifting of the gears. Automatic transmissions are those which do not need a foot clutch.
A continuously automatic transmission device which makes it possible to convert and to transmit power without a clutch by using a combination of differential gears consisting of ring gears, planetary gears and sun gears, is described in U.S. Patent Application Ser. No. 347,916 now U.S. Pat. No. 4,966,575 filed May 5, 1989. Further, another continuous transmission uses a combination of bevel gears and worm gears and is fully described in a U.S. Pat. No. 3,770,879 by Thomas A. W. K. Watson.
However, such transmission devices fail to provide smooth transmission steps and are mechanically complicated. Hence, there is a need for the development of a transmission device which provides excellent capability and which has a relatively simple mechanical structure.
The object of the present invention is to provide a mechanically efficient and continuously variable transmission which is capable of converting and transmitting power to the output shaft in a smooth and stepless while being mechanically simple in design.
A further object of the present invention is to provide a transmission device which rotationally dissipates the rotational driving force transmitted to the input shaft.
A further object of the present invention is to provide a transmission device having a first brake means for gradually applying rotational resistance to a control ring gear to initiate and maintain the rotation of an output shaft and upon further activation of the first brake means to stop the control ring gear such that the rotational speed of the output shaft is further increased.
A further object of the present invention is to provide a transmission device having a second brake means for gradually applying rotational resistance to a high speed control ring gear resulting in an increase in the rotational speed of the output ring gear and upon further activation of the second brake means to stop the rotation of the high speed control ring gear, the rotational speed of the output shaft exceeds the rotational input of input shaft.
To achieve these and other objects, the present invention comprises a combination of planetary gears, sun gears, and ring gears driven by an input shaft to vary the rotational output of the output shaft. A first and a second brake means controls the rotational speed of respective ring gears to initiate and maintain rotational movement of the output shaft and to increase rotational movement of the output shaft, respectively. Upon fully engaging the second brake means and fully disengaging the first brake means, the output shaft can rotate at a greater speed than the input shaft.